Need Help, can't resolve by myself.

Followed all the steps for cleaning system. Norton Antivirus keeps popping up saying there's a trojan horse on my system and it was unable to repair the file/access to the file was denied. Spysweeper also picks up some stuff but it says not all was fixed because an item was running in memory. I spent a whole day on trying to fix it. I've tried running things in safe mode but it doesn't work. There are constant pop ups on my system. What can I do to fix this?